Genomic instability of human BRCA1-mutated, BRCA2-mutated and sporadic control breast tumors. (a) The mean percentage of BAC clones ± S.E.M. with absolute log2 ratio >0.2 is greater in across the 27 BRCA1-mutated tumors (blue) and 28 BRCA2-mutated tumors (orange) compared with 48 sporadic control tumors. P-values are determined by a two-tailed t-test with unequal variance. (b) Each individual tumor aCGH profile was smoothed using KC-SMART (kernel width: 20 Mb). For a range of thresholds, all gains exceeding a positive threshold and losses exceeding the same negative threshold were counted and averaged over each tumor group. Curves are darkened at thresholds for which the average number of CNAs per tumor group is significantly greater in the BRCA1/2-mutated tumors compared with the sporadic control tumors calculated with a two sided t-test with unequal variance, P < 0.05.